Edit HVAC Zone Data - General Tab
Data on this tab is used for controlling the zone internal conditions during the simulation and also for autosizing heating, cooling and outside air equipment related to the zone.
General
Name
This is the name of the building zone with which the current HVAC zone is linked.
Thermostat Schedules
Detailed HVAC Activity data set to 2-Detailed HVAC
If the 2-Detailed HVAC Detailed HVAC Activity data model option is set then you can select schedules defining zone heating and cooling setpoint temperatures on this dialog. Otherwise, if the 1-Simple HVAC option is selected then zone setpoint temperatures and schedules are defined on the Activity and HVAC model data tabs respectively and the Thermostat schedule data is not displayed on this dialog.
Note: The temperatures defined in these schedules must be in °C regardless of whether you are using IP or SI units in the interface.
Thermostat heating setpoint schedule
This is the zone heating temperature schedule. Values in the schedule are temperatures (in °C).
Thermostat cooling setpoint schedule
This is the zone cooling temperature schedule. Values in the schedule are temperatures (in °C).
Comfort PMV Setpoint Schedules
Detailed HVAC Activity data set to 2-Detailed HVAC
If the 2-Detailed HVAC Detailed HVAC Activity data model option is set then you can select schedules which define zone heating and cooling setpoint PMV values on this dialog. Otherwise, if the 1-Simple HVAC option is selected then zone setpoint PMV values and schedules are defined on the Activity and HVAC model data tabs respectively and the Thermostat schedule data is not displayed on this dialog.
The Thermal comfort calculator tool can be used to derive PMV values based on perhaps more familiar parameters.
Heating PMV setpoint schedule
This is the zone heating PMV schedule. Values in the schedule are PMV indices, typically in the range -3 to 3.
Thermostat cooling setpoint schedule
This is the zone cooling PMV schedule. Values in the schedule are PMV indices, typically in the range -3 to 3.
Humidistat Control
Humidistat control
This check-box is used to specify whether or not the zone has humidity control.
Detailed HVAC Activity data is 1-Simple HVAC
If the 1-Simple HVAC option is selected then zone RH setpoints on the Activity tab are used and the demand schedule data on this dialog defines the times when these setpoints operate.
Humidifying demand schedule
This is a schedule that defines the times when humidification may be required. The schedule should have only values of 0 (for times when no humidification is required) or 1 (when humidification to the humidification setpoint defined on the Activity tab is required).
Dehumidifying demand schedule
This is a schedule that defines the times when dehumidification may be required. The schedule should have only values of 0 (for times when no dehumidification is required) or 1 (when dehumidification to the dehumidification setpoint defined on the Activity tab is required).
Detailed HVAC Activity data is 2-Detailed HVAC
If the 2-Detailed HVAC Detailed HVAC Activity data model option is set then you can select schedules defining zone relative humidity setpoints on this dialog.
Humidifying RH setpoint schedule
This is a schedule that defines the humidifying relative humidity setpoint, expressed as a percentage (0-100), for each timestep of the simulation.
Dehumidifying RH setpoint schedule
This is a schedule that defines the dehumidifying relative humidity setpoint, expressed as a percentage (0-100), for each timestep of the simulation.
More information on controlling humidity is available in the Humidity control section.
The rest of the General tab of the HVAC Zone dialog is related to Detailed HVAC autosizing calculations only.
CO2 and Contaminant Control
CO2 and contaminant control
This check-box is used to specify whether or not the zone has CO2 or contaminant control. This must be selected if the zone is to have maximum CO2 or generic contaminant concentration controlled through one of the IAQP DCV methods.
Note: For AHUs with IAQP control at least one connected HVAC zone must have this option selected. This option should not be selected for other types of DCV control.
Detailed HVAC Activity data is 2-Detailed HVAC
If the 2-Detailed HVAC Detailed HVAC Activity data model option is set then you can select schedules defining time-varying CO2 and contaminant setpoints on this dialog.
CO2 control availability schedule
This is a schedule that defines the availability of CO2 control for each timestep of the simulation.
CO2 setpoint schedule
This is a schedule that defines the CO2 setpoint in ppm, for each timestep of the simulation.
Minimum CO2 concentration schedule
This is a schedule that defines the minimum concentration of CO2 in ppm, for each timestep of the simulation.
Generic contaminant control availability schedule
This is a schedule that defines the availability of Generic contaminant control for each timestep of the simulation.
Generic contaminant setpoint schedule
This is a schedule that defines the Generic contaminant setpoint in ppm, for each timestep of the simulation. Enter values between 0 and 1.
More information on DCV is available in the DCV control section of the AHU help page.
The rest of the General tab of the HVAC Zone dialog is related to Detailed HVAC autosizing calculations only.
Cooling Sizing
Cooling design supply air temperature
This is the supply air temperature (in °C or °F) for the zone cooling air flow rate calculation. Air is supplied to the zone at this temperature during the cooling design day simulation; the zone load is met by varying the zone air flow rate. The maximum zone flow rate is used as the zone cooling design air flow rate.
Cooling design supply air humidity ratio
This is the humidity ratio in kilograms of water per kilogram of dry air of the supply air in the zone cooling autosizing air flow rate calculation.
Cooling minimum air flow fraction
This is the minimum zone design cooling volumetric flow rate expressed as a fraction of the zone design cooling volumetric flow rate for VAV systems only. In all cases the maximum flow derived from Cooling minimum flow per zone floor area, Cooling minimum air flow, and Cooling minimum air flow fraction is used to set a minimum supply air flow rate for the zone for VAV systems. The default is zero. This input is currently used in sizing the fan minimum flow rate. It does not affect other component auto-sizing.
Note: This value is only used when the zone is connected to a VAV Air loop, in which case this data is used for sizing and not for the simulation itself.
Zone cooling sizing factor
This is the zone level cooling sizing ratio. The zone design cooling air flow rates and loads will be multiplied by the number input in this field. The default value comes from the Zone group dialog whose default Zone cooling sizing factor is the ASHRAE recommended cooling oversizing factor of 1.15.
Cooling design air flow method
- 1‑Design day means the program will calculate the zone design cooling air flow rate using the zone cooling sizing information and a design day simulation without imposing any limits other than those set by the minimum outside air requirements.
- 2‑Flow/zone means that the program will use the Cooling design air flow rate as the zone design cooling air flow rate.
- 3‑Design day with limit means that the maximum from Cooling minimum flow per zone floor area and Cooling minimum air flow will set a lower limit on the design maximum cooling air flow rate.
Cooling design air flow rate
This is the design zone cooling air flow rate (in m3/s or ft3/min). This setting is only required if Cooling design air flow method is specified as 2‑Flow/zone. This value will be multiplied by the global or zone sizing factor and by zone multipliers.
Cooling minimum flow per zone floor area
This is the minimum zone cooling volumetric flow rate per square meter (units are m3/s-m2). This setting is only required if the Cooling design air flow method is specified as 3‑Design day with limit. In this case it sets a lower bound on the zone design cooling air flow rate. In all cases the maximum flow derived from Cooling minimum flow per zone floor area, Cooling minimum air flow, and Cooling minimum air flow fraction is used to set a minimum supply air flow rate for the zone for VAV systems. The default is 0.000762 m3/s-m2, corresponding to 0.15 cfm/ft2. The applicable sizing factor is not applied to this value.
Cooling minimum air flow
This is the minimum zone cooling volumetric flow rate (in m3/s). This field is used when Cooling design air flow method is specified as 3‑Design day with limit. In this case it sets a lower bound on the zone design cooling air flow rate. In all cases the maximum flow derived from Cooling minimum flow per zone floor area, Cooling minimum air flow, and Cooling minimum air flow fraction is used to set a minimum supply air flow rate for the zone for VAV systems. The default is zero. The applicable sizing factor is not applied to this value.
Heating Sizing
Heating design supply air temperature
This is the supply air temperature (in °C or °F) for the zone heating design air flow rate calculation. Air is supplied to the zone at this temperature during the heating design day simulation, The zone load is met by varying the zone air flow rate. The maximum zone flow rate is used as the zone heating design air flow rate.
Heating design supply air humidity ratio
This is the humidity ratio in kilograms of water per kilogram of dry air of the supply air in the zone heating design air flow rate calculation.
Zone heating sizing factor
This is the zone level heating sizing ratio. The zone design heating air flow rates and loads will be multiplied by the number input in this field. The default value comes from the Zone group dialog whose default Zone heating sizing factor is the ASHRAE recommended heating oversizing factor of 1.25.
Heating design air flow method
There are three options;
- 1‑Design day means the program will calculate the zone design heating air flow rate using the zone heating sizing information and a design day simulation without imposing any limits other than those set by the minimum outside air requirements.
- 2‑Flow/zone means that the program will use the Heating design air flow rate as the zone design heating air flow rate.
- 3‑Design day with limit means that the maximum from Heating maximum flow per zone floor area and Heating maximum air flow will set a lower limit on the design maximum heating air flow rate.
Heating design air flow rate
This is the design zone heating air flow rate (in m3/s or ft3/min). This setting is only required if Heating design air flow method is specified as 2‑Flow/zone. This value will be multiplied by the global or zone sizing factor and by zone multipliers.
Heating maximum flow per zone floor area
This is the maximum zone heating volumetric flow rate per square metre (units are m3/s-m2). This setting is only required if the Heating design air flow method is specified as 3‑DesignDayWithLimit. In this case it sets an upper bound on the zone design heating air flow rate. In all cases the maximum flow derived from Heating maximum flow per zone floor area, Heating maximum air flow, and Heating maximum air flow fraction is used to set a maximum heating supply air flow rate for the zone for VAV systems. The default is 0.002032 m3/s-m2, corresponding to .40 cfm/ft2. This input is not currently used for auto-sizing any of the components.
Heating maximum air flow
This is the maximum zone heating volumetric flow rate in m3/s. This setting is only required if the Heating design air flow method is specified as 3‑Design day with limit. In this case it sets an upper bound on the zone design heating air flow rate. In all cases the maximum flow derived from Heating maximum flow per zone floor area, Heating maximum air flow, and Heating maximum air flow fraction is used to set a maximum heating supply air flow rate for the zone for VAV systems. The default is 0.14158 m3/s, corresponding to 300 cfm. This input is not currently used for auto-sizing any of the components.
Outdoor Air Sizing
When the Detailed HVAC Activity data is set to 1-Simple HVAC then all data under the Outdoor Air Sizing header is disabled and the outdoor air requirement settings are copied from the corresponding building zones' Activity and/or HVAC model data as described below.
When the Detailed HVAC Activity data is set to 2-Detailed HVAC then the outdoor air requirement is defined here on the HVAC zone dialog.
Outdoor air method
There are five options:
Note: If the Detailed HVAC Activity data is set to 1-Simple HVAC then this option is disabled and the Outdoor air method is copied from the corresponding building zones' HVAC model data.
Outdoor air flow per person
This is the design outdoor air flow rate per person for this zone (in m3/s or ft3/min). This setting is only required if either one of the 2‑Flow/person, 4‑Sum, or 5‑Maximum options have been selected for the Outdoor air method. The default is 0.00944 m3/s (20 cfm per person). An outdoor air flow rate is calculated based on the total number of people assigned to the zone. Occupancy schedule values are not applied.
Note: If the Detailed HVAC Activity data is set to 1-Simple HVAC then this option is disabled and the Outdoor air flow per person is copied from Outdoor air flow per person from the corresponding building zones' Activity model data.
Outdoor air flow per zone floor area
This is the design outside air volumetric flow rate per square meter of floor area (in m3/s-m2). This setting is only required if either one of the 3‑Flow/area, 4‑Sum, or 5‑Maximum options have been selected for the Outdoor air method. This value is multiplied by the zone floor area to obtain a flow rate.
Note: If the Detailed HVAC Activity data is set to 1-Simple HVAC then this option is disabled and the Outdoor air flow per zone floor area data is copied from the corresponding building zones' Activity model data.
Outdoor air flow per zone
This is the design outdoor air flow rate for this zone (in m3/s or ft3/min). This setting is only used if either one of the 1‑Flow/zone, 4‑Sum, or 5‑Maximum options have been selected for the Outdoor air method.
Note: If the Detailed HVAC Activity data is set to 1-Simple HVAC then this option is disabled and the flow per zone is calculated from the ac/h value set on the HVAC model data tab and displayed here.